1. Technical Field of the Invention
The invention relates generally to compression testing machines and more particularly to machines applying biaxial compression loads.
2. Description of the Prior Art
There are many types of biaxial compression testing devices available in the prior art. Typically, these devices use two force actuators for applying a biaxial load to a test specimen.
Actuators used include hydraulic pistons and jacks, mechanically and electrically operated screws and the like. In order to produce accurate loading of a test specimen in two directions, relatively complicated testing machines are required. In particular, it is necessary to avoid tangential and torsional loads on the test sample while simultaneously applying specific loads to the test sample in two directions. When it is desired to apply a specific ratio between forces in the two applied directions over a range of load forces, complex hydraulic pressure control or piston sizing is required in testing machines having dual actuators. Likewise, in the jack or screw type machines, the use of dual actuators requires a relatively complicated means of controlling the differential action necessary to produce a specific ratio between the biaxial loads.